Spring balancing device for sliding sash windows and the like



y 1933- H. J. LEAN 1,909,588

SPRING BALANCING DEVICE FOR SLIDING SASH WINDOWS AND THE LIKE Filed June 20, 1930 ....:-W L. Y

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Patented May 16, 1933 UNITED STATES PATENT OFFICE HENRY JAMES LEAN, OF IRENE, NEAR PRETORIA, QTRANSVAAL, UNION OF SOUTH AFRICA, ASSIGN'OR TO UNIVERSAL PATENTS TORIA, SOUTH AFRICA, A CORPORATION OF SOUTH AFRICA SPRING BALANCING DEVICE FOR SLIDING SASI-I WINDOWS AND THE LIKE Application filed. June 20, 1930, Serial No. 462,474, and in the Union This invention relates to a new and improved spring balancing device for sliding sash windows and the like and is particularly suitable for railway or motor coach windows which are apt to slide down owing to the vibration of the vehicle.

A device is at present in use embodying the pantograph or lazy tongs principle actuated by springs attached to the short ends of two 10 levers whose longer ends form the bottom section of the lazy-tongs. The disadvantage of this arrangement is that the arm of leverage 7 of spring tension remains practically constant, thus having less effect when the window is raised to its full height, than when it is in the lowest position. If the spring tension 5 is increased the window tends to remain closed or nearly so and if it is decreased the window will not remain closed 20 but will tend to regain the open position.

This necessitates the use of catches, stops or other devices for fixing the window at the height desired by the passenger.

In my invention I overcome the disadvantage in the above described device in the following manner :-The lower arm of the lever to which the spring is attached is extended in the shape of a curve or series of tangents to a curve, and a roller, to which the spring is attached, is constrained to move either up or down this curved path depending on whether the window is raised or lowered. This has the effect of altering the radius of the point of application of the spring tension in such manner, that the radius or lever arm increases as the spring tension decreases. The weight of the window and sash is by this means supported with a practically constant upward force enabling it to remain stationary at any desired point.

To make the description of this invention more readily understood reference is made to the attached drawing in which Figure 1 is a front elevation of the new method with left hand spring casing cut away to show the spring and attachments.

Figure 2 is a part sectional front elevation of the new lever arm showing details of attachment of spring.

Figure 3 is also a part sectional elevation of South Af-ricaJuly. 4, 1929.

as in Fig. 2, showing the gear in its midway position. i

In Figure 2 the spring 1 is attached by (PROPRIETARY) LIMITED, OF PRE- means of thevshackle8, roller 9' which may have roller or other anti-friction bearings and pin 10 to the lever arm 11 such that when the lever 2 is raised to its topmost position 2 the roller 10 willv be constrained to move along the curved path 1213' until itreaches the position shown by the dotted outline 2, 11, 9. This is the position of the lever when the window which is attached to the bracket 23 is at its highest or closed position. Provision is made in the length of the radius 15 so that when the roller occupies its lowest position 9 the moment about the fulcrum 4 will be slightly in excess of" the amount necessary to provide a balance at that point thus holding the window hard. up in its closed position without the necessity for catches or stops. Similarly the radius 14 may be of such value that the moment about the fulcrum 4 will be-slightl'y less than that required to substain. the weight of the thus ensuring the window remainwindow,

catches ing in its open position without any or fixings. a

In operation the invention functions as follows I V i We startwith the window in its lowest or open position as shown by the position of the spring and levers in full lines in Fig. 1. On commencing to raise the window. the lever 2 will also be raised by means of the connected levers of the pantograph and the position of the curved extension 11 of the lever 2 Fig. 2 will alter in relation to the roller 9' which will take up a new position on the curve 12-13 as soon as the-inclination of the tangent to the curve at that point with the axis 16of' the spring reaches avalue greater than'the angle of friction of the roller 10 with the curvedpath 12-13, Fig. 3; As the window is raised so will the roller 10 continually take up fresh positions onthe-curve 1213 and at each'such positionthe weight of the window will be balanced by the moments of the spring tensions about the various radii of the roller center to fulcrum center. Owing to the unavoidable friction loo between the roller 10 and its path 1213 the position of the lever 2 in relation to the roller 9 will have to alter slightly more than.

the theoretical requirement before the roller will move to a new position as from position of the tangent line 19-20 to that of 17-18 or 21-22 Fig. 8. This provides as is intended an additional advantage since it assures that any slight vibration will not affect the position of the window. A certain amount of adjustment may be made as regards the spring tension by means of the screwed hook bolts 24;

What I claim is 1. A balancing device for a vertically sliding member, comprising a fixed pivot, a lever structure supporting said member and comprising a lever element fulcrumed on the pivot whereby the weight of the member produces in said element a moment about the pivot, said element providing a path of progressively varying radius from the pivot, and spring means pressing on said path to produce a member-supporting moment in said element and mounted to be movable along the path as the element rotates about the pivot and thereby to vary the effective radial component of the member-supporting moment; the radii of the ends of the path being respectively in excess and deficient so that the ratio of the member-supporting moment to the moment produced by the member is greater than unity when the member is at the upper part of its travel and is less than unity when the member is at the lower part of its travel.

2. A balancing device for a vertically sliding member, comprising a fixed pivot, a lever structure supporting said member and comprising a lever element fulcrumed on the pivot whereby the weight of the member produces in said element a moment about the pivot, said element providing a path of progressively varying radius from the pivot, and spring means pressing on said path to produce a member-supporting moment in said element and mounted to be movable along the path as the element rotates about the pivot; said path comprising a number of substantially straight sections with angular junctions in which the spring means tends to lodge.

3. Apparatus as claimed in claim 2, in which the straight sections are parallel to tangents at a few successive spaced points of the path curve which efiects constant equality of the member supporting moment about the pivot and the moment produced about the pivot bythe member.

Signed at Johannesburg, South Africa, this 19 day of May, 1930.

HENRY JAMES LEAN. 

